In a typical hot runner injection molding apparatuses melt flows from a melt source, through a runner manifold, through a set of heated nozzles that are arranged in parallel downstream from the runner manifold, and finally into a set of mold cavities that are positioned in a mold cavity block.
In some apparatuses, there are portions of the melt flow path where the melt loses pressure. Melt flows into these low pressure regions, and remains there due to the pressure gradient between the region and the melt flow path adjacent the region
An example of where such regions can be present is in apparatuses where valve pins are positioned somewhere in the melt flow path for controlling the melt flow. The valve pins are fixed in position, whereas in other cases the valve pin is moveable. Depending on the configuration of the melt flow path relative to the valve pin the valve pin may shield a portion of the melt conduit from the melt flow creating a low pressure region behind the valve pin opposite to where the melt flow encounters the valve pin. As a result of the low pressure region, melt therein can be difficult to remove, which can cause contamination problems when the apparatus is changed over to operate with a new melt composition.
Accordingly, there is a need for a method and device for removing melt from the low pressure region.